The present invention relates to cutting elements of the type which are mounted on rotary drill bits for cutting through earth formations (including rock formations), cement, plugs, etc.
Rotary drilling operations in earth formations are typically carried out using a rotary drill bit which is simultaneously rotated and advanced into the formation. Cutting is performed by cutting elements mounted on the drill bit, and the cuttings are flushed to the top of the bore hole by the circulation of drilling fluid.
A conventional cutting element may comprise a cutting blank mounted on a cemented carbide stud. The blank may include a diamond disk disposed on a carbide substrate. The blank can be braze bonded to an inclined face of the stud, and the stud is then secured, e.g., by press-fit in a recess of the drill bit. Cutting elements of this type are disclosed, for example, in U.S. Pat. No. 4,499,958.
During the use of cutting elements of this type, cutting takes place by means of a section of the peripheral edge of the blank which is brought into contact with the formation being cut.
In the cutting of relatively soft formations, cutting elements with a large cutting area is preferred, whereas cutting elements with a smaller cutting area, e.g., so-called "chisel" cutters, are preferred for cutting harder formations so that the cutting forces can be more concentrated.
Among the problems faced by diamond cutting elements is the deterioration resulting from friction-generated heat. In practice, attempts are made to reduce the temperature of the cutting elements by directing drilling fluid in the vicinity of the cutting elements. It is difficult, however, to apply that fluid directly on the segments of the cutting elements which actually perform the cutting function. Chisel-type cutters are particularly susceptible to thermal deterioration because the cutting action is concentrated on a smaller working area (i.e., so-called point loading) which intensifies the heat build-up in the working area of the diamond.
It would be desirable to reduce the heat build-ups on diamond cutting elements and also increase the rate of formation penetration